Integrated process for the production of high quality motor fuels and heating oils



K. W. LlNN ET AL Sept. 18, 1956 INTEGRATED PROCESS FOR THE PRODUCTION OF HIGH QUALITY MOTOR FUELS AND HEATING OILS Filed Aug. v1s 195s United States Patent O INTEGRATED PROCESS FOR THE PRODUCTION gqFGI-Hlg QUALITY MOTOR FUELS AND HEAT- Karl W. Linn, Fanwood, William M. Smith, Roselle, and Robert L. Greene, Westfield, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application: August 19, 1953, Serial No. 375,106

4 Claims. (CI. 196-28) The present invention is concerned with an improved integrated process for the production of high quality petroleum oil products. The invention is more particularly concerned with an improved integrated hydrofining process for the production of high quality petroleum oil products boiling in the motor fuel and in the heating oil boiling ranges. In accordance with the present invention, one or more feed streams comprising constituents boiling in the motor fuel boiling range and a feed stream boiling in the heating oil boiling range are simultaneously hydroiined in separate reactors wherein the makeup hydrogen for all units is utilized extensively or exclusively in one unit on a once-through basis, and the recycle hydrogen is utilized in thev other units.

It is well known in the art to carry out various opera tions wherein hydrogen is employed for the treatment of various petroleum oil fractions. These operations are normally carried out for such purposes as hydrogenationcracking of high molecular weight aromatic hydrocarbons and for desulfurization. In processes of this character, temperature, pressure, and other operating conditions are such that a considerable portion of the fraction treated is converted to. materials of zlower boiling ranges and viscosities, aniline points. The specific gravities are likewise greatly altered. These changes consume relatively large quantities of hydrogen per barrel of feed. For example, the hydrogen consumption is above about 200 to 600 cubic feet per barrel and up to 3,000 to 4,000 cubic feet per barrel for desulfurization, and for hydrogencracking of aromatics. It lhas now been discovered that if. a particular arrangement and sequence of refining stages be utilized in conjunction with mild hydrofining conditions with respect to different feed streams, unexpected and very desirable results are secured. The process of the present invention may be more fully understood by reference tothe drawing illustrating one embodiment of the same.

Referring specifically to the drawing, a feed fraction boiling in the motor fuel boiling range (100 F. to about 275 F.) is introduced into furnace 1 by means of feedV line 2. The feed stream is heated in furnace 1 to a temperature in the range from about 6007 F. to 750 F., preferably to the range of about. 650 F. to 700 F., with.- drawn by means of line 3, combined with 0.3 to 3.0 volumes of hydrogen per volume of vaporized feed, which is introducedV by means of line 4.

The hydrogen and naphtha are passed through hydroiining zone 5 which is operated as hereinafter described. The hydroned material is withdrawn from zone 5 by means of line 6, passed through a cooling zone 7, wherein the temperature is reduced to a temperature in the range from about 100 F. to 150 F. The cooled stream is removed from cooling zone 7 by means of line 8 and passed into a ash drum 9. Vaporous constituents boiling below about 100 F. and hydrogen are removed overhead from ash drum 9 by means of line 10. A portion of this stream may be purged and removed from the system by means of line 11. The entire stream or a portion thereof ice may be treated with triethanol amine or its equivalent for the removal of hydrogen sulfide in treatingV zone 12. Any portion of the stream to be scrubbed for the removal of H28 is introduced into treating zone 12 by means of line 13. This stream is re-compressed to a pressure in the range from about 200 p. s. i. g. to 250 p. s. i. g. in compression zone 14, and recycled as hereinafter described. The liquid condensate secured in flash drum 9 is withdrawn by means of line 24 and introduced into a stripping zone 25. Temperature and pressure conditions in stripper 25 are adjusted to remove overhead by means of line 26 hydrogen and other low boiling hydrocarbon constituents boiling below about F. A portion of the overhead stream may be purged from the system by means of purge line 27. However, it is preferred to compress these gases in compression zone 28 to a pressure in the range from about to 200 p. s. i. g. The compressed gases are then introduced into line 10. A product stream free of hydrogen and boiling in the range from about 100 F. to 275 F. is removed from. the bottom of stripper 25 by means of line 29 and passed through a re-boiler 30. A portion of this stream is returned to the bottom of tower 25 by means of line 31. The remainder is withdrawn by means of line 32, cooled in cooling zone 33, removed by means of line 34 and passed to a caustic washing and water treating stage.

A virgin naphtha designated as hydroformer feed which preferably boils in the range from about 250 F. to 375 F., is introduced by means of line 16 into furnace zone 15, Where the naphtha is heated to a temperature in the range from about 650 F. to 800 F., preferably in the range from about 700 F. to 800 F. The heated stock is removed from zone 15 by means of line 17 and combined with recycle hydrogen introduced by means of line 18. This feed stock together with the hydrogen is passed through. hydroiining zone 19 which is operated as hereinafter described. The hydroned product is removed from zone 19 by means of line 20,v passed through cooling zone 21 and cooled to a temperature in the range from about 350 F. to 425 F. The cooled stream is removed by means of .line 22 and introduced into a stripping zone 23.

Hydrogen and other hydrocarbon gases boiling below about 300 F. are removed overhead. from zone 23 by means of line 35, cooled in cooling zone 36 and passed to distillate drum 37. At least a portion of the condensed distillate is returned to stripping zone 33 by means of line 38 asreflux. Hydrogen and other gases boiling below about 100 F. are removed from distillate drum 37 by means of line 39 and introduced into line 10 for recycle. In accordance with a preferred adaptationof the invention, the purging of recycle gas for the entire integrated system is done by means ofl line 40.

This is very desirable since this unit is operating with the less volatile of the two aforementioned feed stocks, and it therefore follows that a. lower concentration of constituents which boil in the gasoline range will be present in this fraction. Thus,- the purging of a portion of this gas stream will result in a mini-mum loss of valuable hydrocarbons boiling in the motor fuel boiling range.

A hydrocarbon fraction boiling in the heating oil boiling. range is'. introduced into the system by means of line 41. This fraction is heated in furnace 42 to a temperature of the range from about 600 F. to 675 F. The stream is withdrawn from zone 42 by means of line 43, mixed with fresh makeup hydrogen which is introduced by means of line 44. The combined stream is passed through hydroining zone 45 which is operated as hereinafter described. The hydroiined stream is removed from zone 45 by means of line 46, cooled in cooling zone 47 to a temperature in the range from' about 400 F.- to

475 F. The cool stream is withdrawn by means of line 48 and introduced into the stripper 49. Steam is introduced into stripping zone 49 by means of line 50.

Hydrogen and hydrocarbon constituents boiling below about 500 F. are removed overhead by means of line 51, cooled in zone 52 to a temperature in the range from about 100 F. to 125 F., and passed to distillate drurn 53. Water is removed from distillate drum 53 by means of line 54. A hydrocarbon condensate is removed from zone 53 by means of line 55 and recycled to zone 49. Hydrogen and hydrocarbon constituents boiling below about 100 F. are removed overhead from zone 53 by means of line 55 and passed to recycle line 10.

A liquid product is withdrawn from the bottom of zone 49 by means of line 56, cooled in zone 57 and passed to a caustic washing and water washing zone by means of line 58. In accordance with the present invention, a liquid product is removed from the bottom of zone 23 by means of line 59 and passed to a hydroformer zone 60. Hydroformer zone 60 is operated at a reactor inlet temperature in the range from about 900 F. to l000 F., and at a pressure in the range from about 200 to 800 p. s. i. g., using catalyst as for example, platinum on alumina or molybdenum on alumina. Under these conditions the octane number of the stock is increased and other chemical changes occur resulting in the production of hydrogen which is segregated by means of line 61 and used as makeup hydrogen in hydroiining zone 45.

Furthermore, in accordance with the process of the present invention, a portion of this hydrogen is used as a stripping medium in zone 23 and is introduced by means of line 62. The advantage of using this hydrogen as a stripping medium is that it is dry and sulfur-free. Consequently it is capable of stripping out of the hydroformer feed essentially all of the water and hydrogen sulfide (as well as most of the hydrogen and other hydrocarbon constituents boiling below about 300 F.), which are present in the liquid feed to zone 23. Certain hydroforming catalysts, as for example platinum on alumina, require a dry, sulfur-free feed for satisfactory performance.

By operating as described, wherein the tail or recycle gas is used only in zone and 19, it is possible to use all makeup hydrogen in zone 45, processing the heating oil. Thus, a heating oil of a satisfactory ash point can be secured without the necessity of rerunning the heating oil product, since the makeup hydrogen contains a much lower proportion of low-boiling hydrocarbons.

As pointed out, the invention is particularly concerned with an integrated efficient process for the production of high quality motor fuels and heating oil products. These heating oils are of the nature employed in various burner systems as diesel fuels, or as domestic and industry heating oils. Heating oils may be derived from petroleum by a variety of methods including straight distillation, from crude petroleum oil, and thermal or catalytic cracking of various petroleum oil fractions. Heretofore, in the art, heating oil blends comprised a relatively large proportion of virgin heating oil as compared to cracked heating oils. However, due to the desirability of virgin heating oils as feed stocks to various cracking operations, as for example, a fluid catalytic cracking operation, the blends comprise an increasing proportion of cracked heating oil fractions as compared to virgin stocks. Virgin heating oil fractions are also very desirable as diesel oil products which further decreases their availability for heating oil blends.

It is known in the art that heating oils consisting completely or in part of catalytic cracked stocks are characterized by an undesirable instability giving rise to the formation of sediment. It is also known that when cracked heating oils are blended with sweetened virgin heating oils certain undesirable characteristics are increased due to their incompatibility. As a result, such blended fuel oils tend to cause clogging of filters, orifices, or conduits associated with the burning systems in which they are employed.

It is also known in the art that when a virgin heating oil is blended with a cracked heating oil, the carbon residue of the blend in many cases exceeds the carbon residue of either the virgin heating oil or the cracked heating oil. This carbon residue is an indication of the extent the blended heating oil will carbonize the burners, particularly a rotary burner in actual use and to some extent determines the burning characteristics and desirability of the fuel.

In order to improve the quality of blended heating oils, various processes have been practiced in the art. It is known in the art to process a virgin heating oil by a caustic wash if the oil be relatively sweet. On the other hand, if the virgin heating oil has a relatively high mercaptan content so as to render it sour, the oil is processed by a doctor treat or an equivalent sweetening operation. On the other hand, light cracked heating oils in many operations merely require a caustic wash. However, the conventional procedure is to secure the cracked heating oil from a relatively severe cracking operation in which case it is necessary to acid treat the cracked heating oil followed by a caustic wash in order to control the carbon residue. This latter operation is not desirable since acid treatment polymerizes many desirable constituents resulting in a loss in yield. Furthermore, the sludge is expensive and difcult to handle.

In accordance with the present invention, the instability of catalytically cracked heating oils may be substantially overcome and its compatibility for blending with virgin heating oils increased by subjecting the cracked heating oil fraction to a hydroning operation. Heating oil blends which may be processed by the hydrofining operation of the present invention are particularly hydrocarbon mixtures of which more than about 10%, preferably from about 15% to 60% by volume consist of stocks derived from cracking operations. More precisely still, the nished blends may be characterized as petroleum fractions containing a proportion of cracked stocks greater than 10% preferably from about 15% to 60% by volume, and falling within A. S. T. M. specification D-396-48T for fuel oils (Grades Nos. 1 or 2). Inspections of a typical heating oil blend are for example:

In accordance with the present invention, zones 5 and 19 employ a catalyst comprising cobalt molybdate on alumina. The temperatures in these zones are maintained at about 600 F. and 700 F., respectively, while the pressure is about 200 pounds per square inch. The feed rate is about 8 volumes of oil per volume of catalyst per hour in zone 5 and about 0.5 volume of oil per volume of catalyst per hour in zone 19. The catalyst comprises about 10 to 15 cobalt molybdate on alumina.

The catalyst utilized in reactor 45 processing the heating oil comprises about 5 to 13% molybdenum oxide on alumina. This catalyst is described inldetail below.

The feed rate is about 16 volumes of oil per volume of catalyst per hour.

It is essential, in practicing the present invention that the hydroning-operati-on conducted -on the cracked heating oil lbe a `mild hydroning operation. This is to be distinguished .from .conventional hydroning roperations heretofore practiced in the art. Such hydroning operations have been employed at pressures from 200 to 500 lbs. per square inch, at feed rates of .5 to 2.0 volumes of feed per vo-lume of catalyst per hour. Relatively high rates of hydrogen recycle have been employed, as for example, 2,000 to 4,000 standard cubic feet per barrel in order to prevent carbonization of the catalyst. Likewise, very active catalysts have been used which are eifective for desulfurization. Under these conditions hydrogen consumption has generally been in the range of 150 to 600 standard cubic feet per barrel of feed. This relatively high consumption of hydrogen in the past has made the process expensive to operate, so that its application in the past has been limited to the treatment of relatively high sulfur stocks which could not be desulfurized by any other available treating operation. The catalyst heretofore employed has been a cobalt molybdate supported on a carrier, as for example alumina.

Due to the fact that the sulfur content of heating oils is relatively low, since the cracking operation desulfurizes to a great extent, conventional hydroning operations have not been necessary in the processing of cracked heating oils. On the other hand, when conventional hydroning operations, as described above, were employed in the processing of cracked heating oils for improving the carbon residue, these conventional operations were found entirely unsatisfactory, since they actually increased the carbon residue and further impaired the quality of the fuel. On the other hand, when employing the mild hydroning process of the present invention, unexpected desirable results are secured with a higher quality blended fuel oil product.

The mild hydroning conditions of the present invention may be secured by lowering the temperature, increasing the feed rate per volume of catalyst or by using a less active catalyst. In accordance with the present invention the temperatures used are in the range from about 400 to 700 F., preferably in the range from about 500 to 650 F. Pressures employed are in the range from 50 to 250 lbs. per square inch. The feed rates, in accordance with the present process, are in the range from about 1 to 16 volumes of liquid per volume of catalyst per hour. Preferred feed rates are in the range from 4 to 12 v./v./hr. The hydrogen in the gas to the hydroning unit may vary from 50 to 100%. This means that, for example, dilute hydrogen from a hydroformer can be used in the hydroning process. A particularly desirable method of hydroning in accordance with the present process is to recycle appreciable quantities of hydrogen to the hydroiining unit in order to completely prevent carbonization of the catalyst.

The catalyst utilized in the present invention may com prise known hydroiining catalyst, as for example, cobalt molybdate on a carrier as for example alumina, providing other operating conditions are adjusted to secure a mild hydroning process. The preferred catalyst, however, of the present invention comprises molybdenum oxide on a carrier preferably alumina. The amount of molybdenum oxide employed is about 5 to 13% by Weight based upon the weight o-f the alumina. The catalyst is prepared by known methods, such as lby impregnation of the alumina with a water-soluble molybdenum salt, followed by heating to convert this salt to molybdenum oxide, or by co-precipitation of aluminum and molybdenum hydroxides by addition of an ammoniacal solution of ammonium molybdate to an acid solution of an aluminum salt followed by water `washing and by heating to convert to the oxides. p

It is to be understood that the mild hydroning conditions of `the present invention A'are secured -by the adjustment of the above named operating conditions. For instance, if a .relatively high liquid feed rate is `used as compared to the .amount of catalyst present, the 4higher temperature range maybe employed. On :the other hand, if a very active catalyst is used, .it is :desirable to use a relatively high feed rate or to use a relatively low temperature. The mild hydroning conditions of the present invention are measured by the amount of hydrogen consumption per barrel of oil feed. As pointed out heretofore in the art, conventional hydrofining operations utilized for the desulfurization of certain stocks are conducted under conditions whereby the hydrogen consumption ranges from 150 to 600 standard cubic feet of hydrogen per barrel of oil. These operations used heretofore in the art secured a substantial sulfur reduction (50 to In accordance with the present process, operating conditions are adjusted so that the hydrogen consumption in standard cubic feet per barrel does not exceed 60 and is preferably less than 40. Furthermore, the extent of the sulfur reduction when utilizing the mild hydroning conditions of the present invention does not exceed about 35% and preferably does not exceed about 20%.

Thus, by operating as hereinbefore described, it is possible to include in the recycle gas to zones S and 19 employing cobalt molybdate as the catalyst about 2 to 5% of hydrogen sulde based upon the total volume of recycle gas. This hydrogen sulfide recycle is essential for maintaining activity of the cobalt molybdate catalyst. By employing all the makeup hydrogen from the hydroformer as feed gas to reactor 45, utilizing 5 to 13% molybdena on alumina, it is possible to keep the hydrogen sulfide content, which may be harmful to this particular catalyst, at a minimum.

Furthermore, it is possible to operate reactor 45 at a pressure somewhat higher than that of the other units, as for example at about 230 pounds, such that the tail gas from zone 53 will be at suicient pressure to enter the reactors at zone 5 to 19 without rst being recompressed. Thus, this gas need not be passed through the compressor 14 but may be recycled with the recycle gas after the compressor, thereby saving compressor capacity.

What is claimed is:

1. Improved integrated process for the production of high quality petroleum oil products which comprises mildly hydroin-ing a light naphtha in an initial hydrofining zone, removing the hydroined product from said initial hydroning zone and separating normally gaseous constituents comprising hydrogen from normally liquid hydrocarbons, recycling at least a portion of said normally gaseous constituents to said initial hydroning zone, mildly hydroflning a heavy naphtha in a secondary hydroning zone, removing the hydroned product and separating normally gaseous constituents comprising hydrogen from normally liquid hydrocarbons, recycling `at least a portion of said normally gaseous constituents to said initial and said secondary hydrofining zones, passingsaid normally liquid hydrocarbons from `said secondary hydroning zone hydrofining a petroleum oil boiling in the heating oil -to a hydrotormer whereby hydrogen is formed, mild-ly boiling range in a tertiary hydrofining zone with said formed hydrogen, removing the product from said tertiary hydroiining zone, separating normally gaseous constituents comprising hydrogen from normally liquid hydrocarbons and recycling at least a portion of said latter gaseous constituents .to said initial and said secondary hydroning zones.

2. The process as defined by claim 1 wherein hydrogen is purged from the integrated system by purging a portion of the normally ygaseous constituents secured from said secondary hydroforming zone.

3. Process as defined by claim 2 wherein said light naphtha comprises a fraction boiling in the range from about 100 to 275 F. and wherein said heavy fraction comprises a virgin fraction boiling in the range from about 250 to 375 F.

4. Process as defined by claim 1 wherein a portion of said formed hydrogen is used to segregate said normally gaseous constituents from said liquid hydrocarbons secured from said secondary hydrofining zone.

References Cited in the le of this patent UNITED STATES PATENTS 

1. IMPROVED INTEGRATED PROCESS FOR THE PRODUCTION OF HIGH QUALITY PETROLEUM OIL PRODUCTS WHICH COMPRISES MILDLY HYDROFINING A LIGHT NAPHTHA IN AN INITIAL HYDROFINING ZONE, REMOVING THE HYDROFINED PRODUCT FROM SAID INITIAL HYDROFINING ZONE AND SEPARATING NORMALLY GASEOUS CONSTITUENTS COMPRISING HYDROGEN FROM NORMALLY LIQUID HYDROCARBONS RECYCLING AT LEAST A PORTION OF SAID NORMALLY GASEOUS CONSTITUENTS TO SAID INITIAL HYDROFINING ZONE, MILDLY HYDROFINING A HEAVY NAPHTHA IN A SECONDARY HYDROFINING ZONE, REMOVING THE HYDROFINED PRODUCT AND SEPARATING NORMALLY GASEOUS CONSTITUENTS COMPRISING HYDROGEN FROM NORMALLY LIQUID HYDROCARBONS, RECYCLING AT LEAST A PORTION OF SAID NORMALLY GASEOUS CONSTITUENTS TO SAID INITIAL AND SAID SECONDARY HYDROFINING ZONES, PASSING SAID NORMALLY LIQUID HYDROCARBONS FROM SAID SECONDARY HYDROFINING ZONE HYDROFINING A PETROLEUM OIL BOILING IN THE HEATING OIL 